Firefox could be the real Facebook challenger
readwriteweb.com
readwriteweb.com
I also highly doubt that there are many people anxious to see firefox integrate social networking features. That's the last thing I want them to do, personally. Browsers are platforms. A browser should RUN facebook, not BE facebook. When you try and build software directly into the platform, the results are not pretty. (IE anyone?)
I for one don't want my browser knowing "who I am" - I prefer to let the applications I use know that.
I think Firefox could be better off as an application platform. Let the users decide what they want, make it easy to get and keep the browser slim.